Lysyl hydroxylase (LH), a key enzyme in collagen biosynthesis hydroxylates lysine residues in peptide linkages required in formation of intermolecular cross links essential for a stable collagen structure. Collagen cross links may be important in the age-related changes in connective tissue; they accumulate in aging skin and may be deficient in osteoporosis. Patients with Ehlers-Danlos Syndrome Type VI (EDS VI) an inherited disorder of connective tissue that results from ail deficiency in LH, have clinical features of osteoporosis, hyperextensible skin and joints, and fragile skin. This proposal describes the isolation of a cDNA for LH which will be used to characterize the mutations responsible for LH deficiency in cells isolated from patients with EDS VI. In addition, the LH cDNA will be used to study the mechanism of drug-mediated regulation of LH in normal and LH-deficient fibroblasts. The initial phase of this project will involve isolation of a full length cDNA for LH by screening a recently constructed LH-enriched cDNA library from human skin fibroblasts with a 2.2 Kb probe for human LH, which has been recently isolated by PCR. Sequence information on the cDNA for LH will be used to amplify full length cDNAs, by PCR, from EDS VI strains. Sequencing of certain of these abnormal DNAs should reveal the exact nature of these mutation(s), The regulation of LH will be studied under conditions in which the uniquely-acting drug minoxidil acts to specifically deplete LH activity without affecting prolyl hydroxylase (PH) activity, whereas hydralazine increases both PH and LH levels. The cDNA for LH will be used to probe the regulation of LH under these conditions in both normal and LH-deficient fibroblasts. These experiments will elucidate not only the molecular basis of EDS VI in cultured dermal fibroblasts from human patients but will also provide an understanding of the unique effects of pharmaceuticals such as minoxidil and hydralazine on LH regulation, which may consequently affect the age-related cross links in skin.